I n t e r n a t i o n a l C o u n c i l f o r t h e E x p l o r a t i o n o f t h e S e a
C.M. 1 9 8 7 / ~ : 5 S e s s . 0.
F i s h C a p t u r e Committee
SCHEME FOR DISPLAYING FISH POSITION DATA I N REAL TIME
Kenneth G. Foote
I n s t i t u t e o f Marine R e s e a r c h 5024 Bergen, Norway
ABSTRACT
F i s h r e a c t i o n t o t h e p a s s a g e o f a c o u s t i c s u r v e y i n g v e s s e l s may be a t l e a s t p a r t l y a s s e s s e d t h r o u g h u s e o f t h e a n g l e d a t a d e r i v e d w i t h t h e SIMRAD s p l i t - b e a m e c h o s o u n d e r . S e v e r a l schemes a r e o u t l i n e d f o r d i s p l a y i n g and q u a n t i f y i n g s u c h d a t a i n r e a l t i m e .
R ~ S U M I ~ : PROJET DE VISUALISATION E N TEMPS
REEL
DES D O N N ~ E S SUR LA POSITION DES POISSONSLes r 6 a c t i o n s d e s p o i s s o n s a u p a s s a g e d e s n a v i r e s de p r o s p e c t i o n a c o u s t i q u e p e u v e n t g t r e a u moins p a r t i e l l e m e n t e s t i m e e s p a r l
'
u t i l i s a t i o n d e s donn6es a n g u l a i r e s p r o v e n a n t du s o n d e u r Simrad5
f a i s c e a u s c i n d 6 , P l u s i e u r s p r o j e t s s o n t p r 6 s e n t 6 s p o u r v i s u a l i s e r e t q u a n t i f i e r en temps r P e 1 de t e l l e s donnGes,I n d e t e r m i n i n g t h e t a r g e t s t r e n g t h s o f f i s h , s p l i t - b e a m echo s o u n d e r s o b s e r v e the t a x g e t s s p o s i t i o r i i n t h e beam, 'The p o s i t i o n d a t a a r e a v a i l a b l e i n t h e S I M R A D s p l i t - b e a m echo s o u n d e r i n t h e form o f a l o n g s h i p and
a t h w a r t s h i p a n g l e s (Brede e t al., 1 9 8 7 ) . The a n g l e d a t a have had r a t h e r i . i m i t e d a p p l i c a t i o n r m t i l r e c e n t l . ~ , c o n s i s t i . n g mainly i n beam-mapping e x e r c i s e s (Reynisson 1986, 1 9 8 7 ) , schemes f o r i n t e r p r e t i n g t a r g e t s t r e n g t h d a t a (Begnbol and Lewy l 9 8 7 ) , and t a r g e t - t r a c k i n g i n a f i s h farm (Brede e t aL, 1987)-
Given t h e s t e a d y i n t e r e s t i n f i s h b e h a v i o u r a s i t a f f e c t s measurements o f f i s h d e n s i t y , e s p e c i a l l y b e c a u s e o f t h e p o s s i b i l i t y o f a v o i d a n c e r e a c t i o n s t o t h e p a s s a g e o f t h e s u r v e y v e s s e l (Olsen 1979, 1981, 1987, Olsen e t a l . 1983a and b , Bercy and Bordeau 1987, Diner and Masse 1 9 8 7 , Misund 19871,
t h e r e i s e v e r y r e a s o n t o e x t e n d t h e p r e s e n t u s e s o f a n g l e d a t a . S e v e r a l schemes a r e o u t l i n e d h e r e f o r t h e v i s u a l p r e s e n t a t i o n o f s u c h d a t a . These w i l l p a r t l y q u a n t i f y t h e b e h a v i o u r a l p a t t e r n s o f o b s e r v e d f i s h and, i n some c i r c u m s t a n c e s , a l s o d e t e c t t h e p r e s e n c e o f r e a c t i o n s t o t h e p a s s a g e o f t h e s u r v e y i n g v e s s e l .
THE SCHEMES
Each measurement by t h e s p l i t - b e a m echo s o u n d e r i s c h a r a c t e r i z e d by f i v e d a t a : p i n g number, d e p t h , a l o n g s h i p and a t h w a r t s h i p a n g l e s , and
t a r g e t s t r e n g t h . The a n g l e d a t a a r e c u r r e n t l y u s e d i n t e r n a l l y i n t h e e c h o s o u n d e r t o d e r i v e beam p a t t e r n v a l u e s which, i n t u r n , a r e used w i t h t h e sum-signal o r echo s t r e n g t h v a l u e t o d e t e r m i n e t h e t a r g e t s t r e n g t h . The t a r g e t s t r e n g t h d a t a from a s i n g l e p i n g may be p r e s e n t e d a s a f u n c t i o n o f d e p t h i n an A-scan o v e r a s e l e c t e d d e p t h i n t e r v a l . I f t h e d a t a from e a c h new p i n g a r e p r e s e n t e d a l o n g s i d e t h e p r e v i o u s d a t a , a c o l o u r echogram r e s u l t s . T h i s g i v e s an i m p r e s s i o n o f t h e s p a t i a l and s i z e d i s t r i b u t i o n o f t h e f i s h a l o n g t h e s h i p ' s t r a c k . C o l l e c t i o n o f t h e t a r g e t s t r e n g t h d a t a c o r r e s p o n d i n g t o r e s o l v e d s i n g l e - f i s h e c h o e s i n a h i s t o g r a m q u a n t i f i e s t h e s i z e i n f o r m a t i o n .
Other d a t a p r e s e n t a t i o n s a r e a l s o p o s s i b l e . I n p a r t i c u l a r , t o a s s e s s where t h e o b s e r v e d f i s h a r e i n t h e a c o u s t i c beam, t h e a n g l e d a t a can be p r e s e n t e d d i r e c t l y on a d i s p l a y , a s on a P l a n P o s i t i o n I n d i c a t o r o r PP1
( F o r b e s and Nakken 1 9 7 2 ) . The p a i r o f a n g l e s c h a r a c t e r i z i n g a f i s h p o s i t i o n can d e f i n e a s p o t on an X-Y p l o t o r c i r c l e r e p r e s e n t i n g t h e h o r i z o n t a l c r o s s s e c t i o n o f t h e beam. The a n g l e d a t a from s u c c e s s i v e p i n g s can be c o n t i n u a l l y added t o t h e d i s p l a y u n t i l a c e r t a i n number o f f i s h p o s i t i o n s a r e i n d i c a t e d , when t h e s c r e e n may be c l e a r e d and t h e n e x t p r e s e n t a t i o n begun. A s w i t h t h e c o l o u r echogram, t h e p r e s e n t e d d a t a w i l l be t h o s e f a l l i n g w i t h i n a s p e c i f i e d d e p t h i n t e r v a l .
Four v a r i a n t s o f t h e p r e s e n t a t i o n a r e enumerated, ( l ) Simple s p o t , T h i s i s t h e s i m p l e s t scheme, Each f i s h p o s i t i o n i s r e p r e s e n t e d by a s p o t o f c o n s t a n t s i z e and i n t e n s i t y , (2) Coloured s p o t , The s p o t may be c o l o u r e d o r shaded t o i n d i c a t e t a r g e t s t r e n g t h i n a d d i t i o n t o p o s i t i o n ,
( 3 ) S i z e d s p o t , The s i z e o f t h e s p o t may be coded o r s c a l e d t o i n d i c a t e t h e a s s c c i a t e d t a r g e t s t r e n g t h v a l i l e , ( 4 ) Colouret! and s i z e d s p o t , The t a r g e t s t r e n g t h tlativn i..; coded t w i c e , l;oth by C O L O U ~ iirid by s i z e , -i.n presenting a s p o t , The f i r s t t h r e e schemes a r e i l l u s t r a t e d i n F i g , l for 17 fish e c h o e s with n o n - c o i n c i d e n t a n g l e s ,
I n o r d e r t o q u a n t i f y t h e p o s i t i o n d a t a , h i s t o g r a m s may be formed by c o u n t i n g t h e number o f e c h o e s l y i n g w i t h i n s e c t o r s , s l i c e s o r o t h e r d i v i s i o n s o f t h e beam a n d by normaLizing each t o the r e s p e c t i v e area, Five types a r e shown i n F i g , 2, These a r e d e s c r i b e d a c c o r d i n g t o t h e geometry of t h e
d i v i s i o n . ( l ) S e c t o r s l i c e s . ( 2 ) Alongship s l i c e s . ( 3 ) A t h w a r t s h i p s l i c e s . ( 4 ) S e c t o r t e s s e r a e . The f i r s t geometry i s f u r t h e r d i v i d e d by s u p e r p o s i t i o n of a n n u l i . ( 5 ) R e c t a n g u l a r t e s s e r a e . The second and t h i r d g e o m e t r i e s a r e superimposed t o form a r e c t a n g u l a r g r i d ,
FORE ( a ) Simple s p o t
P O R T
-
STARBOARDA F T ( b ) Shaded s p o t
( c ) S i z e d s p o t
F i g , 1, P r e s e n t a t i o n o f p o s i t i o n s o f r e s o l v e d f i s h e c h o e s i n t h r e e v a r i a n t s , ( a ) Simple s p o t o f c o n s t a n t s i z e . ( b ) c o l o u r e d o r s h a d e d s p o t o f c o n s t a n t s i z e , where t h e c o l o u r o r s h a d i n g i n d i c a t e s t a r g e t s t r e n g t h , i l l u s t r a t e d h e r e by open and c l o s e d c i r c l e s . ( c ) S i z e d s p o t o f f i x e d c o l o u r o r s h a d i n g , b u t w i t h d i a m e t e r i n d i c a t i n g t a r g e t s t r e n g t h .
G E O M E T R Y A G R A P H
FORE FORE /
(a) Sector slices
@
(b) Alongship slices
(c) Athwartship slices
(d) Sector tesserae
(e) Rectangular tesserae
Fig, 2. Geometry of circle subdivisions, with corresponding graphs of area density
Graphs o f f i s h d e n s i t y accompany e a c h o f t h e c i r c l e s u b d i v i s i o n s i n F i g . 2 . I n t h e f i r s t t h r e e c a s e s t h e s e a r e d e s i g n e d t o e l i c i t d i f f e r e n c e s i n f i s h d i s t r i b u t i o n w i t h r e s p e c t t o t h e a c o u s t i c a x i s ( F i g . 2 a ) , d e t e c t l a t e r a l movements o f f i s h away from t h e s h i p ' s t r a c k ( F i g . 2 b ) , and a s s e s s t h e p r e c i s e t i m i n g o f f i s h r e a c t i o n s d u r i n g t h e p a s s a g e o f t h e t r a n s d u c e r p l a t f o r m ( F i g . 2 c ) .
The f o u r t h a n d f i f t h g r a p h s aim t o g i v e a f i n e r s p e c i f i c a t i o n of f i s h d i s t r i b u t i o n . However, s i n c e t h e g r i d i s now two d i m e n s i o n a l , t h e d e n s i t y o f f i s h i n each t e s s e r a can be i n t e n s i t y - o r c o l o u r - c o d e d , o r a t h i r d
p h y s i c a l dimension can be added by p r o j e c t i v e geometry. I n F i g s . 2d and 2 e , i n t e n s i t y - c o d i n g i s i l l u s t r a t e d .
O t h e r graph t y p e s can 'be used. ;Three v a r i a n t s f o r t h e s e c t o r - s l i c e s u b d i v i s i o n a r e shown i n F i g . 3.
I n a l l c a s e s o f q u a n t i f i c a t i o n of a n g l e d a t a , t h e a r e a d e n s i t y o f f i s h s c a t t e r e r s i s t h e s o u g h t q u a n t i t y . Thus t h e number of e c h o e s from r e s o l v e d t a r g e t s w i t h i n e a c h c i r c l e s u b d i v i s i o n must be counted and n o r m a l i z e d by t h e d e f z n e d a r e a .
DISCUSSION
Uses o f t h e p a r t i c u l a r p r e s e n t a t i o n s o f a n g l e d a t a proposed h e r e a r e many. S i n c e t h e s p a t i a l d i s t r i b u t i o n o f r e s o l v e d s i n g l e f i s h i n t h e beam i s p r e s e n t e d , i n h o m o g e n e i t i e s i n t h e d i s t r i b u t i o n w i l l be immediately e v i d e n t . The form o f t h e s e w i l l s u g g e s t t h e manner o f f i s h r e a c t i o n , f o r example, a v o i d a n c e by f l e e i n g away from t h e s h i p ' s t r a c k o r swimming ahead b e f o r e t u r n i n g a s i d e . Examples o f f i s h d i s t r i b u t i o n s on t h e d i s p l a y w i t h t h e s i m p l e - s p o t f o r m a t a r e shown i n F i g , 4 .
I n a d d i t i o n t o g i v i n g i m p r e s s i o n s o f f i s h b e h a v i o u r under s u r v e y i n g c o n d i t i o n s , t h e new schemes can a l s o q u a n t i f y f i s h b e h a v i o u r and r e a c t i o n s t h r o u g h g r a p h s s h o v ~ i n g t h e d e n s i t y of f i s h e c h o e s a c r o s s t h e beam, These may be p r e s e n t e d c o l l a t e r a l l y on t h e p o s i t i o n d i s p l a y , much a s t a r g e t s t r e n g t h h i s t o g r a r i ~ s accompany t h e echogram on -the SI14E7AD s p l i t - - b e a m c o l o u r d i s p l a y .
Storage of the h i s t o g r a m data may allow , s t a . t i s t i c a l . t e s t i n g for d e v i a t i o n s from homogeneity, B y comparing s u c c e s s i v e o r more widely
s e p a r a t e d d a t a s e t s , changes i n f i s h b e h a v i o u r i n t h e c o u r s e o f t h e s u r v e y may be d e t e c t e d . Because t h e n a t u r e o f f i s h r e a c t i o n s undoubtedly v a r i e s w i t h s p e c i e s , a change i n d i s t r i b u t i o n p a t t e r n , whether o b s e r v e d v i s u a l l y by an o p e r a t o r o r d e t e c t e d by a u t o m a t i c p r o c e s s i n g o f t h e d a t a by machine, niay i n d i c a t e a change i n species i n the s u r v e y r e g i o n , Comparison of h i s t o g r a m s computed o v e r t h e same time p e r i o d b u t s e p a r a t e d i n d e p t h may d e m o n s t r a t e depth-dependent r e a c t i o n s , c o n c o m i t a n t s o f t h e b a s i c n o i s e - and L i g h t - s t i m u l i t h e o r i e s o f f i s h r e a c t i o n .
O t h e r p o s s i b l e u s e s of t h e p r e s e n t a t i o n schemes w i l l o c c u r t o t h e i n t e r e s t e d r e s e a r c h e r , a s w i l l v a r i a t i o n s o r developments o f t h e schemes
( a ) S e c t o r Lines
FORE
( b ) Narrow s e c t o r b a r s
(c) Wide s e c t o r ba-rs
F i g . 3. Q u a n t i f i c a t i o n o f d i s t r i b u t i o n s by s e c t o r s l i c e by t h r e e h i s t o g r a m t y p e s .
( a ) Uniform
( b ) L a t e r a l movement
(c) Delayed r e a c t i o n
F i g , 4. Examples o f t h r e e , p o s t u l a t e d s p a t i a l d i s t r i b u t i o n s : ( a ) Uniform, ( b ) L a t e r a l o r a t h w a r t s h i p movement, a s i n f l e e i n g , ( c ) Delayed r e a c t i o n o c c u r i n g e x a c t l y d u r i n g p a s s a g e o f t h e t r a n s d u c e r o v e r t h e f i s h .
t h e m s e l v e s . What s h o u l d be n o t e d p a r t i c u l a r l y i s t h a t t h e i n t r o d u c e d schemes c a n be e f f e c t e d w i t h t h e t e c h n o l o g y t h a t i s a v a i l a b l e a n d i s , i n f a c t , a l r e a d y i n u s e , a s i n t h e SIMRAD s p l i t - b e a m e c h o s o u n d e r . The p r e s e n t a t i o n o f a n g l e d a t a w i l l s i g n i f i c a n t l y e x p a n d o u r knowledge o f f i s h b e h a v i o u r u n d e r s u r v e y i n g c o n d i t i o n s . Q u a n t i f i c a t i o n o f t h e s e d a t a i s i m p o r t a n t b o t h f o r i m p r o v i n g t h e a c c u r a c y o f o u r e s t i m a t e s a n d f o r a t t a c h i n g c o n f i d e n c e l i m i t s t o t h e s e .
REFERENCES
B e r c y , C . , a n d B o r d e a u , B. 1 9 8 7 . P h y s i o l o g i c a l a n d e t h o l o g i c a l r e a c t i o n s o f f i s h t o low f r e q u e n c y n o i s e r a d i a t e d by s o u n d e r s a n d s o n a r s . I n t e r n a t i o n a l Symposium o n F i s h e r i e s A c o u s t i c s , S e a t t l e , W a s h i n g t o n , 22-26 J u n e 1 9 8 7 , 1 4 pp. [mimeo]
B r e d e , R . , K r i s t e n s e n , F. H . , S o l l i , H. a n d Ona, E . 1987. T a r g e t t r a c k i n g w i t h a s p l i t beam e c h o s o u n d e r . I b i d . 20 pp. [mimeo]
Degnbol, P . , a n d Lewy, P. 1 9 8 7 , I n t e r p r e t a t i o n o f t a r g e t s t r e n g t h i n f o r m a t i o n from s p l i t beam d a t a . I b i d . 1 3 pp. [mimeo]
D i n e r , N . , a n d Masse, J . 1987. F i s h s c h o o l b e h a v i o u r d u r i n g e c h o s u r v e y o b s e r v e d b y a c o u s t i c d e v i c e s . I b i d . 1 4 pp. [mimeo]
F o r b e s , S . T . , a n d Nakken, 0.
,
Eds. 1972. Manual o f methods f o r f i s h e r i e s r e s o u r c e s u r v e y a n d a p p r a i s a l . P a r t 2 . The u s e o f a c o u s t i c i n s t r u m e n t s f o r f i s h d e t e c t i o n a n d abundance e s t i m a t i o n . FAO Man. F i s h . S c i.
( 5 ) : 1-138.Misund, 0 . A . 1 9 8 7 . S o n a r o b s e r v a t i o n s o f h o r i z o n t a l e x t e n s i o n , swimming b e h a v i o u r , a n d v e s s e l a n d p u r s e - s e i n e a v o i d a n c e o f h e r r i n g s c h o o l s . I n t . Symp. F i s h . A c o u s t . , S e a t t l e , 22-26 J u n e 1 9 8 7 , 22 p p . [mimeo]
O l s e n , K. 1979. O b s e r v e d a v o i d a n c e b e h a v i o u r i n h e r r i n g i n r e l a t i o n t o p a s s a g e o f a n e c h o s u r v e y v e s s e l . ICES C . M . / B : ~ ~ , 9 p p . [mimeo]
O l s e n , K . 1981. The s i g n i f i c a n c e o f f i s h b e h a v i o u r i n t h e e v a l u a t i o n o f h y d r o a c o u s t i c s u r v e y d a t a , ICES C , M , / B : ~ ~ , 25 pp. [mimeo]
OLsen, K , 198'7, F i s h b e h a v i o u r and a c o u s t i c sampli-ng, I n t , Symp, F i s h , A c o u s t , , S e a t t l e , 22-26 J u n e 1987, 28 p p , [mimeo]
Olsen, K , , A n q e l l , J , , P e t t c r s e n , F , , and L @ v i k , A , 1983a" Observed f i s h r e a c t i o n s t o a s u r v e y i n g v e s s e l wi.th s p e c i a l r e f e r e n c e t o herring, c o d , c a p e l i n and p o l a r c o d . FAO F i s h . Rep. ( 3 0 0 ) :1.3L-L3e,
O l s e n , K . , A n g e l i , J,, a n d LqYvilc, A , j 9 8 3 b , Q u a r i t i t a t i v e estimdtions of t h e i n f l u e n c e o f f i s h b e h a v i o u r on a c o u s t i c a l l y d e t e r m i n e d f i s h a b u n d a n c e , FAO F i - s h , Rep. ( 3 0 0 ) : 1.39-149,
R e y n i s s o n , P . 1 9 8 6 . A c o m p a r i s o n o f two methods f o r m e a s u r i n g t h e e q u i v a l e n t beam a n g l e s o f h u l l mounted t r a n s d u c e r s ( p r e l i m i n a r y ) . I C E S c , M - / B : ~ ~ , 1 4 p p . [mimeo]
R e y n i s s o n , P. 1 9 8 7 . Measurements o f t h e beam p a t t e r n a n d c o m p e n s a t i o n e r r o r s o f s p l i t - b e a m e c h o s o u n d e r s . I n t . Symp. F i s h . A c o u s t . , S e a t t l e , 22-26 J u n e 1 9 8 7 , 1 6 pp. [mimeo]
